Haematological and biochemical aspects of a new family with heterozygous Hb O Padova [alpha 30(B11) Glu----Lys] is described. This variant has been found on a screening programme of abnormal haemoglobin in cord blood. It was separated by cellulose acetate, isoelectric focusing, citrate agar, DEAE-cellulose chromatography and by cation exchange high-performance liquid chromatography. The heat stability and the functional properties were found to be normal. This is the third family with Hb O Padova reported, all from the Mediterranean region.